Abstract 16285: Vectorcardiography for Easy and Reliable Optimization of Av-delay in Patients with Cardiac Resynchronization Therapy
Introduction: Current echocardiographic procedures for optimization of cardiac resynchronization therapy (CRT) are time consuming and subject to noise. We hypothesized that 1) the area of the QRS vector (QRSVarea) reflects total dyssynchrony and that 2) the minimal value of QRSVarea reflects optimal resynchronization and optimal timing of LV stimulation.
Methods: In 11 patients with left bundle branch block (LBBB) and sinus rhythm, implanted with a CRT device for >6 months, LV pacing was applied over a wide range of atrioventricular (AV)-delays (steps of 20ms) during overdrive atrial pacing. At all AV-delays a 3D-vectorcardiogram (VCG, OrtivusAB, Danderyd, Sweden) was recorded, followed by echocardiographic measurements of LV outflow tract velocity time integral (VTI-LVOT) and septal strain (speckle tracking). From the latter septal systolic prestretch (SPS) and rebound stretch (SRS) were assessed as the amount of early systolic stretch and systolic stretch following initial shortening. The minimum of SRS+SPS represents the least abnormal septal contraction.
Results: The figure depicts data from a representative patient. A strong correlation was found between the change in QRSVarea and SPS+SRS at the various AV-delays and between the AV-delays at which both variables reached minimal values (median R=0.89), indicating close electro-mechanical coupling in these failing hearts. Minimal QRSVarea predicted the AV-delay with maximal VTI-LVOT (median difference 20ms; interquatile range (IR) -10 to 40 ms). Difference between actual maximal increase in VTI-LVOT relative to LBBB and VCG-predicted increase was small (-0.4%; IR -1.6 to 0% and -0.5%; IR -1.3 to -0.2% respectively). Correlation (R2) for the fit between actual datapoints and a parabolic optimization curve was considerably higher for QRSVarea (0.91±0.04) than for VTI-LVOT (0.60±0.31).
Conclusions: These data show that VCG analysis may allow easy and accurate optimization of AV-delay for CRT.
- © 2012 by American Heart Association, Inc.